1. Field of the Invention
The invention relates to replaceable filter canister, which may be used with air purifying respirators including air filtration units, gas masks, powered air purifying respirators, breath assist devices, and CBRN systems.
2. Description of the Related Art
Replaceable filter canisters that are shaped to conform to the face of a user are disclosed and claimed in U.S. Pat. No. 7,311,764, which is incorporated herein by reference in its entirety. These filter canisters have a concave outlet wall with a projecting outlet fitting that is adapted to mount to an inlet fitting on a respirator mask. The outlet fittings typically have an external thread that is threadable into an internally threaded fitting on the respirator mask. These replaceable filter canisters, when installed on a respirator mask, sit more closely to the respirator mask than filter canisters that have a relatively flat outlet wall with a projecting outlet fitting. Typical filter canisters that have a relatively flat outlet wall are disclosed in U.S. Pat. No. 5,158,077. These filter canisters are adapted to be installed and removed in the field easily in order to replace spent canisters.
Some purchasers of respirators prefer the conformal filter canisters while other purchasers prefer the traditional flat outlet wall canisters. Therefore, suppliers would have to offer both types of canisters in order to meet all market needs. This market thus requires suppliers to make and inventory both types of canisters. In addition, a purchaser may have to inventory both types of canisters to meet the needs of different conditions.